Three-phase voltage inverter (some questions)

[polibuda]

Homework Statement

Three-phase voltage inverter. How many instantaneous values can: phase-to-phase voltage, phase voltage, control signal, phase current in the case of a symmetrical load RL connected in a star without a neutral conductor? How many combinations of transistors of such a converter are there? Which give the same output voltage?

Relevant Equations

lack

I have no idea how to answer to these questions. Our teacher has given it to solve, but i don't know where I sholud to search informations. Could somebody recommend me valuable sources of knowledge?

 

[berkeman]

I would probably start with a Google Images search on the circuits for 3-phase power inverters, and see where that leads me...